the special senses (eye and ear) chapter 14. 2 overview of the eye eye acts much like a camera...

The Special Senses(Eye and Ear)

CHAPTER 14

2

Overview of the Eye

• Eye acts much like a camera– Lens of eye adjusts to bring object into focus– Pupil of eye constricts to allow less light to

enter in bright setting or dilates to allow more light to enter in darker setting

– Through bending of light rays, image reaches retina

• Sensitive nerve cell layer of eye• Image is transmitted to brain for interpretation

3

• Sclera– White portion of eye

• Tough, fibrous membrane• Maintains shape of eyeball• Serves as protective covering for eye

• Iris– Colored portion of eye

• Pupil– Opening in center of eye– Controls amount of light entering eye

Structures of the Eye(Front View)

4

• Conjunctiva– Thin mucous membrane layer that lines anterior part

of eye and inner part of eyelids• Colorless, but appears white because it covers sclera

• Lacrimal gland– Located at upper outer edge of each eye

• Produces tears

• Lacrimal duct– Located at inner edge of eye

• Tears drain from eye through this duct


5


6

• Eyelids– Continuous with skin and cover the eyeball– Keep surface of eyeball lubricated and protected from

dust and debris through blinking motion

• Eyelashes– Located along edges of eyelids– Help protect eyeball by preventing foreign materials

and/or insects from coming in contact with surface of eyeball


7

Structures of the Eye(Cross Section)

• Sclera– “White of the eye”– Thinnest over anterior surface of the eye– Thickest at the back of the eye, near opening

for optic nerve

• Cornea– Continuous with anterior portion of sclera– Transparent, nonvascular layer covering

colored part of the eye

8

• Conjunctiva– Mucous membrane lining inner surfaces of

eyelids and outer surfaces of eye

• Choroid– Vascular middle layer of eye

• Just beneath sclera• Contains extensive capillaries that provide blood

supply and nutrients to eye• Contains the iris, ciliary body, and suspensory

ligaments


9

• Iris– Colored portion of eye

• Can be seen through transparent corneal layer

• Pupil– Located in center of iris

• Controls amount of light entering eye

• Lens– Colorless biconvex structure that aids in

focusing images clearly on retina


10

• Ciliary body– Located on each side of the lens– Contains muscles responsible for adjusting lens to

view near objects

• Suspensory ligaments– Radiate from ciliary body and attach to lens– Hold lens in place– Assist in adjusting shape of lens for proper focusing of

eye


11

• Retina– Sensitive nerve cell layer

• Changes energy of light rays into nerve impulses• Transmits nerve impulses via optic nerve to brain

for interpretation of image seen by eye

– Nerve cells of retina• Rods are responsible for vision in dim light and for

peripheral vision• Cones responsible for visualizing colors, central

vision, and vision in bright light


12

• Retina – Macula Lutea

• Oval, yellowish spot near center of retina

– Fovea Centralis• Small depression located within macula lutea• Sharpest image is obtained when image focuses

directly on fovea centralis = central vision


13

• Optic nerve– Receives impulses from retina and transmits

them to the brain• Images are then interpreted as vision

• Optic disc– Contains no rods or cones– Known as the “blind spot” of the eye– Center of optic disc serves as point of entry

for artery that supplies retina


14


Lateral Cross Section of the Eye

15

• Anterior cavity of the eye– Anterior chamber

• Located in front of lens• Filled with clear, watery fluid called aqueous humor

– Posterior chamber• Located behind lens• Also filled with aqueous humor • Flows back and forth between both chambers


16

• Posterior cavity of eye– Posterior to lens– Filled with vitreous humor

• Clear, jellylike substance that gives shape to the eyeball

• Not constantly reproduced• Blindness can result if vitreous humor escapes

from eye


17

Process of Vision

• Process begins as light rays enter eye– Transmitted through cornea, aqueous humor,

pupil, lens, and vitreous humor to retina• Sensitive nerve cells of retina transmit image

through optic nerve to brain• Brain interprets image as vision

18

Process of Vision• Refraction

– Process of bending of light rays as they pass through the various structures of the eye to produce a clear image on the retina

• Errors of refraction – Occur when eyeball is abnormally shaped– Occur when lens has lost ability to

accommodate to near vision• Vision will be blurred• Can be adjusted with corrective lenses

PATHOLOGICAL CONDITIONS

The Eye

20

Astigmatism

• Pronounced– (ah-STIG-mah-tizm)

• Defined– Refractive error causing light rays entering the

eye to be focused irregularly on the retina due to an abnormally shaped cornea

• Correction: contact lenses or eyeglasses to neutralize defect

21

Blepharitis

• Pronounced– (blef-ah-RYE-tis)

• Defined– Inflammation of the eyelid margins stemming

from seborrheic, allergic, or bacterial origin

22

Blepharoptosis(Ptosis)

• Pronounced– (blef-ah-roh-TOH-sis)

• Defined– Occurs when eyelid partially or entirely covers

the eye as a result of a weakened muscle

23

Blepharoptosis

Blepharoptosis

24

Blindness

• Pronounced– (BLINDNESS)

• Defined– Absence of vision or the need for assistive

devices and/or assistance from others to accomplish daily activities due to inability to see

25

Monochromatism (Color Blindness) • Pronounced

– (mon-oh-KROH-mah-tizm)

• Defined– Inability to sharply perceive visual colors

• Daltonism– Unable to distinguish greens from reds

• Achromatic Vision – Cannot distinguish any color; perceives only white, gray,

and black

26

Cataract

• Pronounced– (KAT-ah-rakt)

• Defined– Lens in the eye becomes progressively cloudy

losing its normal transparency• Alters perception of images due to interference of

light transmission to retina

27

Chalazion

• Pronounced– (kah-LAY-zee-on)

• Defined– Cyst or nodule on eyelid resulting from an

obstruction of a meibomian gland, which is responsible for lubricating margin of the eyelid

28

Conjunctivitis, Acute

• Pronounced– (kon-junk-tih-VYE-tis acute)

• Defined– Inflammation of mucous membrane lining the

eyelids and covering the front part of the eyeball

– Also called “Pinkeye”

29

Corneal Abrasion

• Pronounced– (COR-nee-al ah-BRAY-zhun)

• Defined– Disruption of the cornea’s surface epithelium

commonly caused by an eyelash, a small foreign body, contact lenses, or a scratch from a fingernail

30

Diabetic Retinopathy

• Pronounced– (dye-ah-BET-ik reh-tin-OP-ah-thee)

• Defined– Condition that occurs as a consequence of an

8 to 10-year duration of diabetes mellitus in which the capillaries of retina experience scarring

31

Diabetic Retinopathy

• Causes of retinal capillary scarring– Abnormal dilation and constriction of vessels– Hemorrhages– Microaneurysms– Abnormal formation of new vessels causing

leakage of blood into the vitreous humor• Leakage causes permanent decline in sharpness

of vision

32

Ectropion

• Pronounced– (ek-TROH-pee-on)

• Defined– “Turning out” or eversion of the eyelash

margins from the eyeball leading to exposure of the eyelid and eyeball surface and lining

• Occurs especially in the lower eyelid

33

Entropion

• Pronounced– (en-TROH-pee-on)

• Defined– “Turning in” of the eyelash margins resulting

in the sensation similar to that of a foreign body in the eye (redness, tearing, burning, and itching)

• Occurs especially in the lower margins

34

Exophthalmia

• Pronounced– (eks-off-THAL-mee-ah)

• Defined– Abnormal protrusion of the eyeball(s) usually

with the sclera noticeable over the iris– Typically due to an expanded volume of

orbital contents

35

Glaucoma

• Pronounced– (glau-KOH-mah)

• Defined– Ocular disorders identified as a group due to

the increase in intraocular pressure

36

Glaucoma• Chronic open-angle glaucoma

– Primary disorder– Breakdown in drainage system of the

circulation of aqueous humor• Gradual elevation of internal pressure leads to

decreased blood supply to optic nerve and retina• Peripheral vision is gradually lost when untreated

37

Glaucoma• Acute closed-angle glaucoma

– Mouth of drainage system is narrow and closes completely

– Allowing no flow of aqueous humor• Rapid occurrence characterized by severe pain,

blurred vision, photophobia, redness, and seeing “halos” around light

• If untreated, person can lose his or her sight within several days

38

Hemianopia

• Pronounced– (hem-ee-an-NOP-ee-ah)

• Defined– Loss of vision or blindness in one-half of the

visual field

39

Hordeolum (Stye)

• Pronounced– (hor-DEE-oh-lum)

• Defined– Bacterial infection of an eyelash follicle or

sebaceous gland– Originating with redness, swelling, and mild

tenderness in margin of eyelash

40

• Pronounced– (high-per-OH-pee-ah)

• Defined– Refractive error in which the lens of the eye

cannot focus on an image accurately– Results in blurred vision due to light rays

focused behind the retina because eyeball is shorter than normal

• Also called farsightedness

Hyperopia

41

Hyperopia

Hyperopia (Farsightedness)

42

Hyphema (Hyphemia)

• Pronounced– (high-FEE-mah)

• Defined– Bleed into anterior chamber of eye – Resulting as a postoperative complication or

from a blunt eye injury

43

• Pronounced– (kair-ah-TYE-tis)

• Defined– Corneal inflammation caused by a

microorganism, trauma to eye, a break in sensory innervation of cornea, hypersensitivity reaction, or a tearing defect

– May be due to dry eyes or ineffective eyelid closure

Keratitis

44

Myopia

• Pronounced– (my-OH-pee-ah)

• Defined– Refractive error in which the lens of the eye

cannot focus on an image accurately– Resulting in blurred distant vision due to light

rays focused in front of retina because eyeball is longer than normal

• Also known as nearsightedness

45

Myopia

Myopia (nearsightedness)

46

• Pronounced– (nik-tah-LOH-pee-ah)

• Defined– Inadequate vision at night or in faint lighting

following reduction in synthesis of rhodopsin– Compound in rods of retina that enables the

eye to adjust to low-density light

Nyctalopia(Night Blindness)

47

• Pronounced– (niss-TAG-mus)

• Defined– Vertical, horizontal, rotary, or mixed rhythmic

involuntary movements of the eye(s)• Caused by use of alcohol or certain drugs, lesions

on the brain or inner ear, congenital abnormalities, nerve injury at birth, or abnormal retinal development

Nystagmus

48

• Pronounced– (off-THAL-mee-ah nee-oh-nay-TOR-um)

• Defined– Purulent (contains pus) inflammation of

conjunctiva and/or cornea in newborn• Cause of the keratitis and conjunctivitis results

from newborn’s exposure to viral, bacterial, chemical, or chlamydial agents

Ophthalmia Neonatorum

49

Presbyopia

• Pronounced– (prez-bee-OH-pee-ah)

• Defined– Refractive error occurring after age of 40– Lens of the eye(s) cannot focus on an image

accurately due to loss of elasticity • Also called farsightedness due to better clarity of

distant objects

50

• Pronounced– (ter-IJ-ee-um)

• Defined– Irregular growth developing as a fold in the

conjunctiva– Usually on nasal side of the cornea– Disrupts vision if it extends over pupil

• Can be caused by allergies and excessive ultraviolet light exposure

Pterygium

51

Pterygium

Pterygium

52

Retinal Detachment• Pronounced

– (RET-in-al detachment)

• Defined– Partial or complete splitting away of the retina

from the pigmented vascular layer called the choroid, interrupting vascular supply to the retina and thus creating a medical emergency

53

Retinal Tear

• Pronounced– (RET-in-al tear)

• Defined– Opening in retina that allows leakage of

vitreous humor

54

• Pronounced– (skleh-RYE-tis)

• Defined– Presence of inflammation in the white,

outside covering of the eyeball, the sclera• Symptoms include intense redness with dull pain

and possibly some loss of vision

Scleritis

55

Scotoma

• Pronounced– (skoh-TOH-mah)

• Defined– Defined area in one or both eyes– Decreased visual function

56

Strabismus

• Pronounced– (strah-BIZ-mus)

• Defined– Failure of eyes to gaze in same direction due

to weakness in muscles controlling position of eye

• Most common type is nonparalytic strabismus• Inherited defect in which the eye position of the

two eyes has no relationship

57

Strabismus

• Convergent Strabismus– Also known as “Crosseye” – Also known as “Esotropia”– Affected eye turns inward

• Usually develops in infancy or early childhood

58

Strabismus

• Divergent Strabismus– Also known as “Walleye”– Also known as “Exotropia”– Affected eye turns outward

59

Strabismus

Strabismus(A) Convergent(B) Divergent

60

• Pronounced– (sin-EK-ee-ah)

• Defined– Adhesion in eye that develops as a

complication of trauma or surgery– Secondary condition of one of the following

pathological conditions: cataracts, glaucoma, keratitis, or uveitis

• Adhesion causes the iris to adhere to lens or cornea

Synechia

61

Trachoma

• Pronounced– (tray-KOH-mah)

• Defined– Infectious eye disease caused by Chlamydia

trachomatis– Chronic and will lead to blindness without

treatment• Early symptoms include tearing, pain,

photophobia, and inflammation

62

• Pronounced– (yoo-vee-EYE-tis)

• Defined– Inflammation of all or part of middle vascular

layer of eye made up of the iris, ciliary body, and choroid

• Characterized by blurred vision, pain, redness, pupillary constriction, and intense photophobia

Uveitis

DIAGNOSTIC TECHNIQUES, TREATMENTS

AND PROCEDURES

The Eye

64

• Corneal transplant– Surgical transplantation of a donor cornea

(cadaver’s) into the eye of a recipient usually under local anesthesia

• Electronystagmography– Group of tests used in evaluating vestibule-

ocular reflex• Normal reflex produced by stimulation of

vestibular apparatus in which eye position compensates for motion of the head

Diagnostic Techniques, Treatments, and Procedures

65

• Electroretinogram (ERG)– Recording of changes in electrical potential of

retina after stimulation of light

• Extracapsular Cataract Extraction (ECCE)– Surgical removal of anterior segment of lens

capsule along with lens allowing for insertion of an intraocular lens implant


66

• Fluorescein staining– Application of a fluorescein-stained sterile

filter paper strip moistened with a few drops of sterile saline or sterile anesthetic solution to the lower cul-de-sac of the eye to visualize a corneal abrasion


67

• Gonioscopy– Process of viewing anterior chamber angle of

eye for evaluation, management, and classification of normal and abnormal angle structures

– Intraocular lens implant• Surgical process of cataract extraction and

insertion of an artificial lens in patient’s eye– Restores visual acuity and provides improved depth

perception, light refraction, and binocular vision


68

• Iridectomy– Extraction of a small segment of the iris to

open an anterior chamber angle and permit the flow of aqueous humor between the anterior and posterior chambers

– Relieves person’s intraocular pressure


69

• Keratoplasty– Transplantation of corneal tissue from one

human eye to another to improve vision in affected eye

• Also called corneal grafting


70

• Laser in situ Keratomileusis (LASIK)– LASIK procedure is a form of laser vision

correction for nearsightedness (myopia)

• Ophthalmoscopy– Examination of external and internal structures

of the eye– Utilizes an ophthalmoscope


71


• Pachymetry– Measures thickness of cornea

• Patient’s eyes are numbed • Uses an ultrasonic-wave instrument to gauge

thickness of each cornea

72

• Phacoemulsification– Removing a lens by using ultrasound

vibrations to split up lens material into tiny particles that can be suctioned out of the eye

• Photo Refractive Keratectomy– Surgical procedure in which a few layers of

corneal surface cells are shaved off by an “excimer laser beam” to flatten cornea and reduce myopia or nearsightedness


73

• Retinal Photocoagulation– Surgical procedure using an argon laser to

treat conditions such as retinal detachment, and diabetic retinopathy

• Retinal Detachment – argon laser used to create an area of inflammation, which will develop adhesions, causing a welding of the layers

• Diabetic Retinopathy – argon laser used to seal microaneurysms and areas of leakage, and to reduce risk of hemorrhage


74


• Slit-Lamp exam– Examination of external and internal

structures of the eye using a low power microscope combined with a high-intensity light source focused to shine as a slit beam

• Also known as biomicroscopy

75

• Tonometry– Process of determining intraocular pressure

by calculating resistance of eyeball to an applied force causing indentation

• Trabeculectomy– Surgical excision of a portion of corneoscleral

tissue to decrease intraocular pressure in persons with severe glaucoma

Diagnostic Techniques,Treatments, and Procedures

76

• Trabeculoplasty– Surgical creation of a permanent fistula used to

drain fluid (aqueous humor) from the eye’s anterior chamber

– Usually performed under general anesthesia• Laser trabeculoplasty is an outpatient plastic

surgery approach used in management of glaucoma


77

Overview of the Ear

• Two important functions of the ear– Enables us to hear– Sensory organ of balance or equilibrium

• Location of one ear on each side of head produces binaural hearing– Hearing from both sides

78

• External ear– Visible portion not contained within the head– Auricle or pinna

• Cartilaginous flap or ear lobe

– External auditory canal• Tube leading from auricle to the middle ear• Lined with tiny hairs called cilia to aid in transmitting

sound waves inward

– Tympanic membrane (eardrum)• Separates external ear from middle ear

Structures of the Ear

79

• Middle ear– Three tiny bones known as auditory ossicles– Malleus

• Resembles shape of a hammer• Connected to tympanic membrane and transmits

sound vibrations to second auditory ossicle

– Incus• Resembles shape of an anvil• Transmits sound vibrations from malleus to third

auditory ossicle


80

• Middle ear – Stapes

• Shaped like a tiny stirrup• Transmits sound vibrations from incus to inner ear

– Eustachian tube• Connects middle ear to pharynx• Auditory tube

– Oval window• Separates middle ear from inner ear• Base of stapes fits into oval window


81

• Inner ear– Vestibule

• Central portion of inner ear• Located next to stapes and between cochlea and

semicircular canals• Contains utricle and saccule-membranous

pouches or sacs that aid in maintaining balance

– Cochlea• Snail-shaped bony structure• Contains endolymph and perilymph• Auditory fluids that aid in transmission of sound

vibrations


82

• Inner ear – Organ of Corti

• True organ of hearing• Contained within the cochlea• Here, sound vibrations are converted into nerve

impulses that are transmitted to the brain for interpretation as hearing

– Semicircular canals• Located behind the vestibule• Three bony, fluid-filled loops that help to maintain

one’s balance


83


84

The Process of Hearing

Pathway of soundvibrations

PATHOLOGICAL CONDITIONS

The Ear

86

Cholesteatoma

• Pronounced– (koh-lee-stee-ah-TOH-mah)

• Defined– Slow-growing cystic mass made up of

epithelial cell debris and cholesterol found in the middle ear

• Occurs as a congenital defect or as a result of chronic otitis media

87

Deafness, Conductive

• Pronounced– (Deafness kon-DUK-tiv)

• Defined– Hearing loss caused by breakdown of the

transmission of sound waves through the middle and/or external ear

88

Deafness, Sensorineural

• Pronounced– (Deafness sen-soh-ree-NOO-ral)

• Defined– Hearing loss caused by inability of nerve

stimuli delivered to brain from inner ear due to damage in auditory nerve or cochlea

89

Impacted Cerumen

• Pronounced– (Impacted seh-ROO-men)

• Defined– Excessive accumulation of waxlike secretions

from glands of external ear canal

90

Labyrinthitis

• Pronounced– (lab-ih-rin-THIGH-tis)

• Defined– Infection or inflammation of the labyrinth or

the inner ear– Specifically, the three semicircular canals in

the inner ear– Fluid-filled chambers and control balance

91

Mastoiditis

• Pronounced– (mass-toyd-EYE-tis)

• Defined– Inflammation of mastoid process– Usually an acute expansion of an infection in

the middle ear – Otitis media

92

Ménière's Disease

• Pronounced– (may-nee-ARYZ dih-ZEEZ)

• Defined– Chronic inner ear disease– Over accumulation of fluid in the labyrinth– Characterized by recurring episodes of

vertigo, hearing loss, feeling of pressure or fullness in the affected ear, and tinnitus

93

Otitis Externa (O.E.) (Swimmer’s Ear)

• Pronounced– (oh-TYE-tis eks-TER-nah)

• Defined– Inflammation of outer or external ear canal

• Result of growth of bacteria or fungi in external ear• Major symptom is pain, especially when the ear is

tugged on, along with a red swollen ear canal

94

Otitis Media, Acute (A.O.M.)

• Pronounced– (oh-TYE-tis MEE-dee-ah)

• Defined– Middle ear infection– Predominately affects infants, toddlers, and

preschoolers

95

Serous Otitis Media (S.O.M.)

• Pronounced– (SEER-us oh-TYE-tis MEE-dee-ah)

• Defined– Collection of clear fluid in middle ear that may

follow acute otitis media or be due to an obstruction of eustachian tube

96

• Pronounced– (SOO-per-ah-tiv oh-TYE-tis MEE-dee-ah)

• Defined– Purulent collection of fluid in the middle ear– Person may experience pain (possibly

severe), an elevation in temperature, dizziness, decreased hearing, vertigo, and tinnitus

– Also called acute otitis media

Suppurative Otitis Media

97

Otosclerosis

• Pronounced– (oh-toh-sklair-OH-sis)

• Defined– Condition in which footplate of stapes

becomes immobile and secured to oval window

– Results in a hearing loss

98

Perforation of Tympanic Membrane

• Pronounced– (per-for-AY-shun of the tim-PAN-ik

membrane)

• Defined– Rupture of tympanic membrane or eardrum

DIAGNOSTIC TECHNIQUES, TREATMENTS,

AND PROCEDURES

The Ear

100


• Audiometry – Process of measuring how well an

individual hears various frequencies of sound waves

• Otoscopy– Use of an otoscope to view and examine

tympanic membrane and various parts of outer ear

101

• Tuning Fork Test (Rinne Test)– Examination that compares bone

conduction and air conduction

• Tuning Fork Test (Weber Test)– Examination used to evaluate auditory

acuity as well as discover whether a hearing deficit is a conductive loss or a sensorineural loss


102

• Otoplasty– Removal of a portion of ear cartilage to bring

pinna and auricle near head

• Stapedectomy– Microsurgical removal of stapes diseased by

otosclerosis– Typically under local anesthesia


103

• Hearing aids– Devices that amplify sound to provide

precise perception and interpretation of words • In-canal style – fits completely into ear canal• In-ear style – worn in external ear• Behind-ear style – placed behind ear• Body hearing aid – sound delivered to ear canal

by way of microphone


104

• Myringotomy– Surgical procedure with insertion of a small

ventilation tube into inferior segment of tympanic membrane

• Tympanotomy– Also called a myringotomy


105

• Myringoplasty– Surgical repair of the tympanic membrane

with a tissue graft after a spontaneous rupture that results in hearing loss

• Tympanoplasty– Also called a myringoplasty


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